Sheep anti-Membrane-associated guanylate cyclase of inverted orientation-3, Guanylate Kinase-WW domains,c-erbB-2 is a receptor tyrosine kinase. It exhibits extracellular domains with two cysteine-rich sequences, and a cytoplasmic tyrosine kinase domain flanked by large hydrophilic tails that carry several tyrosine autophosphorylation sites. Approximately 25 % of primary breast and ovarian tumors were found to overexpress the protein.